Water jet cutting machines have cutting heads equipped with nozzles that direct high pressure and high velocity jets of water to cut and drill workpieces. Intensifiers are used to increase the pressure of water to an ultra high pressure range of 60,000 to 100,000 psi or more. An example of a high pressure intensifier for producing a high velocity fluid jet stream is shown in U.S. Pat. No. 3,811,795. The ultra high pressure water is delivered to the cutting heads and discharged through nozzles as water jets which cut workpieces. Abrasive materials are introduced into the water flowing through the cutting heads in some waterjet cutting machines to increase the cutting action of the water jets. Examples of waterjet cutting machines are disclosed in U.S. Pat. Nos. 3,997,111 and 4,380,138.